1. Field of the Invention
The present invention relates the field of ophthalmology, and particularly to crossed haptics for intraocular lenses ("IOL"), the haptics being suitable for implantation of an appropriate optic in either a phakic or an aphakic eye.
2. Description of the Related Art
Ophthalmologists have been developing the art of implanting an artificial lens in the human eye for many years, both to replace the natural lens which has been removed due to disease (an aphakic eye), and to supplement the natural lens with a corrective lens (a phakic eye).
Various pathologic disease processes can cause deterioration of the natural lens requiring removal of the lens, most notably the opacification of the lens which occurs in cataracts. In the developmental stage, cataracts may be treated by frequent changes of eyeglass prescription. When useful vision is lost, the natural lens is generally removed, either intact or by emulsification. When the lens has been removed, correction is achieved either through spectacles, contact lenses, or an intraocular implant.
Common vision problems include myopia (nearsightedness) hypermetropia (hyperopia or farsightedness) and astigmatism. Traditionally such vision problems have been treated with corrective lenses in spectacles or contact lenses. However, as significant improvements and experience has been gained, the use of intraocular implants using corrective lenses has increased.
Generally, the lens separates the aqueous humor from the vitreous body. The iris separates the region between the cornea or anterior of the eye and the lens into an anterior chamber and a posterior chamber. The lens itself is contained in a membranes known as the capsule or capsular sac. When the lens is removed from the eye, the capsule may also be removed (intracapsular excision), or the anterior portion of the capsule may be removed with the lens leaving the posterior portion of the capsule intact (extracapsular extraction), often leaving small folds or flaps from the anterior portion of the capsule. In an intraocular implant, the artificial or prosthetic lens may be inserted in the anterior chamber, the posterior chamber, or the capsular sac. The artificial lenses are usually fixedly attached within the eye, either by stitching to the iris, or by some supporting means or arms attached to the lens, often in the form of sweeping arms called haptics.
Examples of lens for implantation in the anterior chamber include: U.S. Pat. No. 4,254,509, issued Mar. 10, 1981 to Jerald L. Tennant (an accommodating lens with 2 haptics 180.degree. apart arched posteriorly to optic, with an arc at the end of each haptic defining feet); U.S. Pat. No. 4,816,032, issued Mar. 28, 1989 to Jens G. Hetland (optic with a hole in the center to equalize pressure and prevent glaucoma, having 2 loop haptics); and Soviet Invention Certificate No. SU 1377086, published Nov. 4, 1986 (optic with two pairs of crossed haptics).
An example of a lens for implantation in the posterior chamber is shown in U.S. Pat. No. 5,108,429, issued Apr. 28, 1992 (optic with concentric support ring attached by micromotors controlled by computer to adjust the position of the lens for loss of focal power or astigmatism resulting from the surgery).
A number of advances have dealt with implants in the capsular bag, which attempt to take advantage of the capsular membrane too avoid damage to the tissue of the eye. Among them are: U.S. Pat. No. 4,711,638, issued Dec. 8, 1987 to Richard L. Lindstrom (2 haptics attached to one quadrant of optic, forming semicircles on opposite sides of the optic, and open ended 180.degree. from their point of attachment); U.S. Pat. No. 4,795,460, issued Jan. 3, 1989 to Aziz Y. Anis (2 haptics circumferentially surrounding optic by about 350.degree., attached to the optic 180.degree. apart); U.S. Pat. No. 4,804,361, issued Feb. 14, 1989, also to Anis (optic surrounded by supporting ring connected to optic by two elongated, curved members); U.S. Pat. No. 4,842,600, issued Jun. 27, 1989 to Fred T. Feaster (a single haptic overlapping itself with a noose at the end for guiding the haptic); U.S. Pat. No. 4,863,463, issued Sep. 5, 1989 to Tik T. Tjan (optic with concentric supporting ring attached by two elongated, curved members); U.S. Pat. No. 4,878,911, issued Nov. 7, 1989 to Aziz Y. Anis (optic with concentric supporting ring connected by 2 straight segments 180.degree. apart); U.S. Pat. No. 5,171,320, issued Dec. 15, 1992 to Okihiro Nishi (optic with grooves on periphery receiving anterior flaps of capsule); U.S. Pat. No. 5,266,074, issued Nov. 30, 1993 to Nishi, et al. (same as above, but with different shapes for periphery); U.S. Pat. No. 5,366,501, issued Nov. 22, 1994 to David W. Langerman (optic with two concentric support rings attached by straight bars, the outer ring angled anteriorly); U.S. Pat. No. 4,655,775, issued Apr. 7, 1987 to Thomas J. Clasby III (optic with ridges to offset optic from posterior surface of posterior chamber, having 2 bent haptics); and U.S. Pat. No. 4,950,290, issued Aug. 21, 1990 to William Kammerling (lens to reduce posterior capsular opacification, having biconvex optic with helically shaped loop haptic sloping 10.degree. anterior to the optic).
Examples of correcting lenses are described in U.S. Pat. No. 4,585,456, issued Apr. 29, 1986 to John M. Blackmore (corrective lens in contact with natural lens, having 2 appendages or haptics fitting into the ciliary sulcus); U.S. Pat. No. 4,769,035, issued Sep. 6, 1988 to Charles D. Kelman (corrective lens with folding optic and two broad haptics 180.degree. apart, each having an arc at the free end to define feet, the optic being folded and inserted in the posterior chamber through the pupil); U.S. Pat. No. 5,098,444, issued Mar. 24, 1992 to Fred T. Feaster (optic glued to anterior surface of natural lens); U.S. Pat. No. 5,258,025, issued Nov. 2, 1993 to Fedorov, et al. (optic with same radius of curvature as natural lens, two broad haptics having feet fitting in Zinn's zonules); U.S. Pat. No. 5,480,428, issued Jan. 2, 1996, also to Fedorov, et al. (corrective lens floating in the eye); and our own pending application (a deformable intraocular corrective lens with 2 curved haptic 180.degree. apart).
Examples of accommodating lenses are shown in U.S. Pat. No. 5,443,506, issued Aug. 22, 1995 to Antoine L. Garabet (varying the power of the lens by a fluid loop through a first optic, the fluids having differing refractive indices and responding to electrical impulses from the ciliary body); U.S. Pat. No. 5,489,302, issued Feb. 6, 1996 to Bernt C. Skottun (lens with fluid and membranes responding to change in pressure caused by ciliary muscle, changing volume of fluid and refractive index of lens).
U.S. Pat. No. 4,573,998, issued Mar. 4, 1986 to Thomas P. Mazzocco, describes various arrangements of haptics, none of which are crossed, and various methods for implanting deformable intraocular lenses, none of which describe using a viscoelastic material to join seriated sutures. U.S. Pat. No. 4,994,080, issued Feb. 19, 1991 to Dennis P. Shepard, shows an optic with at least one opening to improve focusing for depth, with embodiments having either 2 or 4 haptics, none being crossed. U.S. Pat. No. 5,522,890, issued Jun. 4, 1996 to Nakajima, et al., discloses a deformable lens having two haptics attached to the optic using right angled reinforcements at the periphery of the optic which are thicker than the periphery, the lens being folded into a tube shape for implantation in the eye.
Some foreign patents showing slightly different arrangements of the haptics include: U.K. Patent. No. 2,124,500, published Feb. 22, 1984 (annular ring attached to optic by fibers); German Patent No. 3,722,910, published Jan. 19, 1989 (two haptics, each having a substantially quarter moon shape); French Patent No. 2,653,325, published Apr. 26, 1991 (an annular haptic bound to haptic by a bridge, and 180.degree. away by a convex loop); French Patent No. 2,666,503, published Mar. 13, 1992 (two haptics joining optic on the same side, extending in semicircle on opposite side of optic, and having a stop to prevent crossing of haptics); German Patent No. 4,030,005, published Mar. 26, 1992 (two haptics spreading out from a common bridge to optic); and French Patent No. 2,687,304 published Aug. 20, 1993 (optic with annular support ring joined to optic by two bridges).
Despite the advances, there remain problems with intraocular implants which may be ameliorated by the improved haptics and method of releasing the haptics of the present invention inside the bulb of the eye. When an intraocular lens is inserted in the eye, an incision is made in the cornea or sclera. The incision causes the cornea to vary in thickness, leading to an uneven surface which causes astigmatism. The insertion of a rigid lens through the incision, even with compressible haptics, requires an incision large enough to accommodate the rigid lens (at least 6 mm), and carries with it the increased risk of complications, such as infection, laceration of the ocular tissues, and retinal detachment. Deformable intraocular lenses made from polymethylmethacrylate ("PMMA"), polysulfone, silicone or hydrogel may be inserted through a smaller incision, about 4 mm.
Nevertheless, it is critical that the lens be properly centered and properly fixed so that it does not slip out of position. In an anterior chamber implant, the lens should be positioned between the cornea and the iris, but avoiding contact with either to prevent corneal damage, proliferation of corneal epithelium on the anterior surface of the lens causing opacification, or iritis. If the lens is not positioned properly with respect to the pupil, too much light may be admitted to the retina, causing serious vision difficulties. The haptics or lens support generally lodge in the angle of the anterior chamber, but it is desirable that the haptics be as flexible as possible while keeping the area of surface contact between the haptic and the eye tissue as small as possible to avoid swelling, laceration, infection, or other damage to the eye tissue.
The anterior chamber of the eye is filled with the aqueous humor, a fluid secreted by the ciliary process, passing from the posterior chamber to the anterior chamber through the pupil, and from the angle of the anterior chamber it passes into the spaces of Fontana to the pectinate villi through which it is filtered into the venous canal of Schlemm. The lens must be positioned so the flow of fluid is not blocked or glaucoma may result. If the haptics fit slightly too tight, the patient experiences pain and the lens may have to be removed. If the haptics are slightly too loose, the lens may move into the endothelial cells on the inside of the cornea causing permanent loss of vision.
Posterior chamber and capsular bag implants involve both similar and different considerations. In posterior chamber implants, the haptics normally lodge in the ciliary sulcus, entailing the same considerations with regard to tissue swelling and damage through laceration. Most posterior chamber implants are placed in the posterior capsule in order to take advantage of the insulating properties of the capsule membrane. Here, it is desirable to stretch the capsule as much as possible, vaulting the optic posteriorly to avoid having the anterior flaps proliferate and opacify the anterior surface of the lens, and to stretch the capsule taut. The corrective lens for the phakic eye must be extremely thin in order to fit into the limited space in either the anterior or posterior chambers with the natural lens still in place, but must have some area of thickness at the periphery of the lens to support attachment of the haptics.
Regardless of the type of implant, some means of centering the implant is essential. Currently artificial lenses are implanted using special tools to compress the haptics, such as forceps or cannulas, or rely on microhooks to manipulate the optic through a hole in the surface of the optic. Haptics designed to center in the eye and means for compressing the haptics without the use of bulky tools during centering is therefore desirable.
The present invention solves these problems by a deformable intraocular lens having two pairs of crossed haptics with footplates connected to the optic by a stem. The lens is inserted into the eye using a unique method of compressing the haptics by seriated sutures temporarily joined using a viscoelastic material, which is dissolved after centering the lens in the eye.
Although the Soviet Invention Certificate SU 1,377,086 also shows crossed haptics, it is noted that (1) the optic is rigid, requiring a longer incision (6 mm) and the increased risk of complications during insertion, as well as restricting use to anterior chamber implants; (2) the haptics do not have footplates, placing more surface area of the haptic in contact with the eye tissue; (3) there is no stem between adjacent haptics, but rather each haptic is individually attached to the haptic, requiring the periphery of the lens to be thick enough for attachment of the haptics; and (4) the haptics extend outwardly from the optic for 3/4 of their length before turning concavely towards the lens, virtually precluding compressing the haptics either in front of or behind the lens, presenting a longer profile for insertion through the incision.
Thus, none of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Hence the crossed haptics for intraocular lenses solving the aforementioned problems is desired.